WIP: Rewrite export-html with tree sidebar, client-side rendering

- Add tree sidebar with search and filter (Default/All/Labels)
- Client-side markdown/syntax highlighting via vendored marked.js + highlight.js
- Base64 encode session data to avoid escaping issues
- Reuse theme.ts color tokens via getResolvedThemeColors()
- Sticky sidebar, responsive mobile layout with overlay
- Click tree node to scroll to message
- Keyboard shortcuts: Esc to reset, Ctrl/Cmd+F to search

packages/coding-agent/src/config.ts

@@ -60,6 +60,21 @@ export function getThemesDir(): string {
 	return join(packageDir, srcOrDist, "modes", "interactive", "theme");
 }
 
+/**
+ * Get path to HTML export template directory (shipped with package)
+ * - For Bun binary: export-html/ next to executable
+ * - For Node.js (dist/): dist/core/export-html/
+ * - For tsx (src/): src/core/export-html/
+ */
+export function getExportTemplateDir(): string {
+	if (isBunBinary) {
+		return join(dirname(process.execPath), "export-html");
+	}
+	const packageDir = getPackageDir();
+	const srcOrDist = existsSync(join(packageDir, "src")) ? "src" : "dist";
+	return join(packageDir, srcOrDist, "core", "export-html");
+}
+
 /** Get path to package.json */
 export function getPackageJsonPath(): string {
 	return join(getPackageDir(), "package.json");